U.S. patent number 7,175,949 [Application Number 11/356,518] was granted by the patent office on 2007-02-13 for radiation-sensitive compositions and imageable materials.
This patent grant is currently assigned to Eastman Kodak Company. Invention is credited to Scott A. Beckley, Nicki R. Miller, Ting Tao, Paul R. West.
United States Patent |
7,175,949 |
Tao , et al. |
February 13, 2007 |
Radiation-sensitive compositions and imageable materials
Abstract
A negative-working radiation-sensitive composition includes a
polymeric binder comprising a polymer backbone and having attached
thereto a carbazole derivative represented by the following
Structure (I): ##STR00001## wherein Y is a direct bond or a linking
group, and R.sup.1 to R.sup.8 are independently hydrogen, or an
alkyl, alkenyl, aryl, halo, cyano, alkoxy, acyl, acyloxy, or
carboxylate groups, or any adjacent R.sup.1 through R.sup.8 groups
can together form a carbocyclic or heterocyclic group or a fused
aromatic ring. The composition can be sensitive to radiation having
a maximum wavelength of from about 150 to about 1500 nm, and can be
used to prepare negative-working imageable elements that be imaged
and developed as lithographic printing plates.
Inventors: |
Tao; Ting (Fort Collins,
CO), West; Paul R. (Fort Collins, CO), Beckley; Scott
A. (Windsor, CO), Miller; Nicki R. (Ft. Collins,
CO) |
Assignee: |
Eastman Kodak Company
(Rochester, NY)
|
Family
ID: |
37719626 |
Appl.
No.: |
11/356,518 |
Filed: |
February 17, 2006 |
Current U.S.
Class: |
430/17; 430/905;
430/910; 430/325; 430/281.1; 430/302; 430/278.1 |
Current CPC
Class: |
G03F
7/029 (20130101); G03F 7/031 (20130101); G03F
7/033 (20130101); B41C 1/1008 (20130101); Y10S
430/106 (20130101); Y10S 430/111 (20130101); B41C
2210/06 (20130101); B41C 2210/22 (20130101); B41C
2210/24 (20130101); B41C 2210/26 (20130101); B41C
2210/04 (20130101) |
Current International
Class: |
G03F
7/032 (20060101); G03F 7/031 (20060101); G03F
7/033 (20060101); G03F 7/30 (20060101) |
Field of
Search: |
;430/17,281.1,278.1,302,325,905,910 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Belfield et al (Eds), Photoinitiated Polymerization, Hua and
Crivello, "Photosensitization of Onium Salt Initiated Cationic
Photopolymerizations by Carbazole Monomers, Polymers, and
Oligomers" ACS 2003, pp. 219-231. cited by other.
|
Primary Examiner: Schilling; Richard L.
Attorney, Agent or Firm: Tucker; J. Lanny
Claims
The invention claimed is:
1. A radiation-sensitive composition comprising: a radically
polymerizable component, an initiator composition capable of
generating radicals sufficient to initiate polymerization of said
radically polymerizable component upon exposure to imaging
radiation, a sensitizing dye, and a polymeric binder comprising a
polymer backbone and having attached thereto a carbazole derivative
represented by the following Structure (I): ##STR00008## wherein Y
is a direct bond or a linking group, and R.sup.1 to R.sup.8 are
independently hydrogen, or an alkyl, alkenyl, aryl, halo, cyano,
alkoxy, acyl, acyloxy, or carboxylate groups, or any adjacent
R.sup.1 through R.sup.8 groups can together form a carbocyclic or
heterocyclic group or a fused aromatic ring.
2. The composition of claim 1 wherein Y is a direct bond, and
R.sup.1 to R.sup.8 are independently hydrogen or alkyl groups
having 1 to 8 carbon atoms or halo groups.
3. The composition of claim 2 wherein each of R.sup.1 to R.sup.8 is
hydrogen.
4. The composition of claim 1 wherein said sensitizing dye has a
.lamda..sub.max of from about 650 to about 1500 nm.
5. The composition of claim 1 wherein said sensitizing dye has a
.lamda..sub.max of from about 150 to about 650 nm.
6. The composition of claim 5 wherein said sensitizing dye is
represented by the Structure G-(Ar.sub.1).sub.3 or
Ar.sub.1-G-Ar.sub.2 wherein Ar.sub.1 and Ar.sub.2 are the same or
different, substituted or unsubstituted carbocyclic aryl group, and
G is a furan, oxazole, or oxadiazole ring, or Ar.sub.2 can also be
an arylene-G-Ar.sub.1 or arylene-G-Ar.sub.2 group.
7. The composition of claim 6 wherein said sensitizing dye has
Structure G-(Ar.sub.1).sub.3 wherein each of said Ar.sub.1 is
substituted with a primary, secondary, or tertiary amine.
8. The composition of claim 1 wherein said radically polymerizable
component comprises comprises an ethylenically unsaturated
polymerizable group or a crosslinkable ethylenically unsaturated
group.
9. The composition of claim 1 wherein said initiator composition
comprises a triazine compound, peroxide, 2,4,5-triarylimidazolyl
dimer, an onium salt, oxime ether or ester, N-phenyl glycine or
derivative thereof, anilinodiacetic acid or derivative thereof,
thiol compound, or combinations thereof of two or more of these
compounds.
10. The composition of claim 1 wherein said initiator composition
comprises an organic boron salt, iodonium, sulfonium, an
s-triazine, or a combination of two or more of these compounds.
11. The composition of claim 1 wherein said initiator composition
is present in an amount of from about 0.5 to about 30%, said
radically polymerizable component is present in an amount of from
about 10 to about 70%, said sensitizer is present in an amount of
from about 1 to about 20%, said polymeric binder is present in an
amount of from about 10 to about 90%, all percentages based on
composition total solids.
12. The composition of claim 1 wherein said polymeric binder has a
number average molecular weight of from about 1,000 to about
1,000,000 and an acid value of from about 5 to about 400 mg KOH/g,
and is represented by the following Structure (II): ##STR00009##
wherein A represents recurring units comprising the carbazole
derivative represented by Structure (I), B represents recurring
units derived from ethylenically unsaturated polymerizable monomers
that do not comprise a carbazole derivative, x is from about 0.1 to
about 99.9 mol %, and y is from about 0.1 to about 99.9 mol % based
on total recurring units.
13. The composition of claim 12 wherein B represents recurring
units derived from one or more (meth)acrylamides, (meth)acrylates,
(meth)acrylonitrile, (meth)acrylic acid, styrenic monomer,
N-substituted maleimides, vinyl acetate, maleic anhydride, or
2-hydroxyethyl methacrylate, x is from about 5 to about 50 mol %,
and y is from about 50 to about 95 mol %, and said polymeric binder
has a number average molecular weight of from about 5,000 to about
100,000 and an acid number of from about 10 to about 200 mg
KOH/g.
14. A negative-working imageable element comprising a substrate
having thereon an imageable layer comprising: a radically
polymerizable component, an initiator composition capable of
generating radicals sufficient to initiate polymerization of said
radically polymerizable component upon exposure to imaging
radiation, a sensitizing dye, and a polymeric binder comprising a
polymer backbone and having attached thereto a carbazole derivative
represented by the following Structure (I): ##STR00010## wherein Y
is a direct bond or a linking group, and R.sup.1 to R.sup.8 are
independently hydrogen, or an alkyl, alkenyl, aryl, halo, cyano,
alkoxy, acyl, acyloxy, or carboxylate groups, or any adjacent
R.sup.1 through R.sup.8 groups can together form a carbocyclic or
heterocyclic group or a fused aromatic ring.
15. The element of claim 14 wherein said substrate is a phosphoric
acid anodized, poly(acrylic acid)-treated aluminum substrate or a
sulfuric acid anodized, phosphate/fluoride-treated aluminum
substrate.
16. The element of claim 14 wherein said sensitizing dye has a
.lamda..sub.max of from about 750 to about 1200 nm, said radically
polymerizable component comprises comprises an ethylenically
unsaturated polymerizable group or a crosslinkable ethylenically
unsaturated group and said initiator composition comprises an
iodonium borate salt, sulfonium, or s-triazine, or a combination of
two or more these compounds.
17. The element of claim 14 wherein said sensitizing dye has a
.lamda..sub.max of from about 150 to about 750 nm, said radically
polymerizable component comprises an ethylenically unsaturated
polymerizable group or a crosslinkable ethylenically unsaturated
group and said initiator composition comprises a triazine compound,
peroxide, 2,4,5-triarylimidazolyl dimer, an onium salt, oxime ether
or ester, N-phenyl glycine or derivative thereof, anilinodiacetic
acid or derivative thereof, thiol compound, or a combination of two
or more these compounds.
18. The element of claim 14 wherein said initiator composition is
present in an amount of from about 0.5 to about 30%, said radically
polymerizable component is present in an amount of from about 10 to
about 70%, said sensitizer is present in an amount of from about 1
to about 20%, said polymeric binder is present in an amount of from
about 10 to about 90%, all percentages based on dry imageable layer
weight.
19. The element of claim 14 wherein said polymeric binder has a
number average molecular weight of from about 1,000 to about
1,000,000 and an acid value of from about 5 to about 400 mg KOH/g,
and is represented by the following Structure (II): ##STR00011##
wherein A represents recurring units comprising the carbazole
derivative represented by Structure (I), B represents recurring
units derived from ethylenically unsaturated polymerizable monomers
that do not comprise a carbazole derivative, x is from about 0.1 to
about 99.9 mol %, and y is from about 0.1 to about 99.9 mol %,
based on total recurring units.
20. The element of claim 19 wherein B represents recurring units
derived from one or more (meth)acrylamides, (meth)acrylates,
(meth)acrylonitrile, (meth)acrylic acid, styrenic monomer,
N-substituted maleimides, vinyl acetate, maleic anhydride, or
2-hydroxyethyl methacrylate, x is from about 5 to about 50 mol %,
and y is from about 50 to about 95 mol %, and said polymeric binder
has a number average molecular weight of from about 5,000 to about
100,000 and an acid number of from about 10 to about 200 mg
KOH/g.
21. The element of claim 14 wherein said initiator composition
comprises an iodonium borate salt when said sensitizer has a
.lamda..sub.max of from about 750 to about 900 nm or a
hexaarylbisimidazole when said sensitizer has a .lamda..sub.max of
from about 150 to about 650 nm, said radically polymerizable
component is derived from the reaction of a multifunctional
isocyanate compound and one or more urea urethane or urethane
(meth)acrylates comprising carboxy groups, and said polymeric
binder comprises recurring units derived from N-vinyl
carbazole.
22. A method of making a negative-working printing plate
comprising: A) imagewise exposing an imageable element comprising a
substrate having thereon an imageable layer comprising: a radically
polymerizable component, an initiator composition capable of
generating radicals sufficient to initiate polymerization of said
radically polymerizable component upon exposure to imaging
radiation, a sensitizing dye, and a polymeric binder comprising a
polymer backbone and having attached thereto a carbazole derivative
represented by the following Structure (I): ##STR00012## wherein Y
is a direct bond or a linking group, and R.sup.1 to R.sup.8 are
independently hydrogen, or an alkyl, alkenyl, aryl, halo, cyano,
alkoxy, acyl, acyloxy, or carboxylate group, or any adjacent
R.sup.1 through R.sup.8 groups can together form a carbocyclic or
heterocyclic group or a fused aromatic ring, to form both imaged
and non-imaged regions in said imageable layer, B) developing said
imagewise exposed imageable layer to remove only said non-imaged
regions, and C) optionally baking said imagewise exposed element
after step A.
23. The method of claim 22 wherein said imagewise exposing step A
is carried out using radiation having a maximum wavelength of from
about 700 to about 1200 nm.
24. The method of claim 22 wherein said imagewise exposing step A
is carried out using radiation having a maximum wavelength of from
about 150 to about 700 nm, and said imageable element optionally
including an oxygen-impermeable overcoat disposed over said
imageable layer.
25. An imaged element obtained from the method of claim 22.
Description
FIELD OF THE INVENTION
This invention relates to radiation-sensitive compositions and
imageable elements such as negative-working printing plate
precursors. More particularly, it relates to highly sensitive
radiation-sensitive compositions and imageable elements that can be
imaged at a wavelength of from about 150 to about 1500 nm. The
invention also relates to methods of using these imageable elements
to provide, for example, lithographic printing plates.
BACKGROUND OF THE INVENTION
Radiation-sensitive compositions are routinely used in the
preparation of imageable materials including lithographic printing
plate precursors. Such compositions generally include a
radiation-sensitive component, an initiator system, and a binder,
each of which has been the focus of research to provide various
improvements in physical properties and thereby imaging
performance.
Recent developments in the field of printing plate precursors
concern the use of radiation-sensitive compositions that can be
imaged by means of lasers or laser diodes, and more particularly,
that can be imaged and/or developed on-press. Laser exposure does
not require conventional silver halide graphic arts films as
intermediate information carriers (or "masks") since the lasers can
be controlled directly by computers. High-performance lasers or
laser-diodes that are used in commercially-available image-setters
generally emit radiation having a wavelength of at least 700 nm,
and thus the radiation-sensitive compositions are required to be
sensitive in the near-infrared or infrared region of the
electromagnetic spectrum. However, other useful radiation-sensitive
compositions are designed for imaging with ultraviolet or visible
radiation.
There are two possible ways of using radiation-sensitive
compositions for the preparation of printing plates. For
negative-working printing plates, exposed regions in the
radiation-sensitive compositions are hardened and unexposed regions
are washed off during development. For positive-working printing
plates, the exposed regions are dissolved in a developer and the
unexposed regions become an image.
Negative-working radiation-sensitive compositions and imageable
elements are described for example, in U.S. Pat. No. 6,309,792
(Hauck et al.), U.S. Pat. No. 6,569,603 (Furukawa et al.), and U.S.
Pat. No. 6,899,994 (Huang et al.), and EP 1,182,033 (Fujimako et
al.) and EP 1,449,650 (Goto).
Problem to be Solved
U.S. Pat. No. 4,774,163 (Higashi) describes photopolymerizable
compositions containing a carbazole derivative and optionally a
linear polymer binder for photoresists and printing plate
preparation.
While many known negative-working radiation sensitive compositions
have found usefulness in the industry, there continues to be a need
to improve photosensitivity. In addition, known negative-working
imageable elements often require a pre-heat step after imagewise
exposure and before development in order to enhance the
crosslinking within the imageable layer.
There is a desire in the industry to reduce processing steps where
possible including the conventional pre-heat step. There is also a
need to have compositions of this type that can be imaged using a
variety of imaging devices at various wavelengths from 150 to 1500
nm.
SUMMARY OF THE INVENTION
The present invention provides a radiation-sensitive composition
comprising:
a radically polymerizable component,
an initiator composition capable of generating radicals sufficient
to initiate polymerization of the radically polymerizable component
upon exposure to imaging radiation,
a sensitizing dye, and
a polymeric binder comprising a polymer backbone and having
attached thereto a carbazole derivative represented by the
following Structure (I):
##STR00002## wherein Y is a direct bond or a linking group, and
R.sup.1 to R.sup.8 are independently hydrogen, or an alkyl,
alkenyl, aryl, halo, cyano, alkoxy, acyl, acyloxy, or carboxylate
group, or any adjacent R.sup.1 through R.sup.8 groups can together
form a carbocyclic or heterocyclic group or a fused aromatic
ring.
This invention also provides a negative-working imageable element
comprising a substrate having thereon an imageable layer comprising
the radiation-sensitive composition described above.
This invention also provides a method of making a negative-working
printing plate comprising:
A) imagewise exposing an imageable element of this invention (for
example, as described above),
to form both imaged and non-imaged regions in the imageable
layer,
B) developing the imagewise exposed imageable layer to remove only
the non-imaged regions, and
C) optionally baking the imagewise exposed element after step
A.
Also provided by this invention are imaged elements that are
obtained from the method described above.
The present invention provides a number of advantages. The
negative-working radiation-sensitive compositions and imageable
elements can be designed to be sensitive and imageable at any
wavelength of from about 150 to about 1500 nm by choosing
appropriate sensitizing dyes. Thus, imaging can be carried out
using ultraviolet (UV) or visible radiation, and alternatively
using infrared radiation (IR). In addition, a pre-heat step is not
needed and improved sensitivity (digital speed) and durability to
imaging radiation is achieved by using a particular binder
containing pendant carbazole groups represented by Structure I.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a graphical representation of Optical Density vs.
Exposure Energy (mJ/cm.sup.2) data as described in Examples 1 4
below.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
As used herein, "acid number" is the number of milligrams of KOH
required to neutralize the free acid groups in one gram of the
substance (for example, a radically polymerizable component or
polymeric binder, as described below).
Unless the context indicates otherwise, when used herein, the term
"radiation-sensitive composition", "imageable element", and
"printing plate precursor" are meant to be references to
embodiments of the present invention.
In addition, unless the context indicates otherwise, the various
components described herein such as "polymeric binders",
"sensitizing dyes", "radically polymerizable component", "polymeric
binder", and similar terms also refer to mixtures of such
components. Thus, the use of the article "a" is not necessarily
meant to refer to only a single component.
Moreover, unless otherwise indicated, percentages refer to percents
by dry weight.
For clarification of definitions for any terms relating to
polymers, reference should be made to "Glossary of Basic Terms in
Polymer Science" as published by the International Union of Pure
and Applied Chemistry ("IUPAC"), Pure Appl. Chem. 68, 2287 2311
(1996). However, any definitions explicitly set forth herein should
be regarded as controlling.
The term "polymer" refers to high and low molecular weight polymers
including oligomers and includes homopolymers and copolymers.
The term "copolymer" refers to polymers that are derived from two
or more different monomers.
The term "backbone" refers to the chain of atoms in a polymer to
which a plurality of pendant groups are attached. An example of
such a backbone is an "all carbon" backbone obtained from the
polymerization of one or more ethylenically unsaturated
polymerizable monomers. However, other backbones can include
heteroatoms wherein the polymer is formed by a condensation
reaction or some other means.
Radiation-Sensitive Compositions
One aspect of the present invention is a radiation-sensitive
composition that may have any utility wherever there is a need for
a coating that is polymerizable using suitable electromagnetic
radiation, and particularly where it is desired to remove unexposed
regions of the coated and imaged composition. The
radiation-sensitive compositions can be used in photomask
lithography, photoresists, imprint lithography, microelectronic and
microoptical devices, printed circuit boards, paints, and molding
compositions. Preferably, they are used to prepare negative-working
lithographic printing plate precursors and imaged lithographic
printing plates that are defined in more detail below.
The radically polymerizable component present in the
radiation-sensitive composition contains any polymerizable group
that can be polymerized using free radical initiation. For example,
the radically polymerizable component can contain an addition
polymerizable ethylenically unsaturated group, a crosslinkable
ethylenically unsaturated group, a ring-opening polymerizable
group, an azido group, an aryldiazonium salt group, an
aryldiazosulfonate group, or a combination thereof.
Suitable ethylenically unsaturated compounds that can be
polymerized or crosslinked include ethylenically unsaturated
polymerizable monomers that have one or more of the polymerizable
groups, including unsaturated esters of alcohols, such as acrylate
and methacrylate esters of polyols. Oligomers and/or prepolymers,
such as urethane acrylates and methacrylates, epoxide acrylates and
methacrylates, polyester acrylates and methacrylates, polyether
acrylates and methacrylates, and unsaturated polyester resins can
also be used.
Particularly useful radically polymerizable components comprise
addition polymerizable ethylenically unsaturated groups having
multiple acrylate and methacrylate groups and combinations thereof
such as polyfunctional acrylate and methacrylate monomers. Examples
of such compounds include, but are not limited to, 1,4-butanediol
diacrylate, 1,6-hexanediol, neopentylglycol diacrylate,
tetraethyleneglycol diacrylate, trisacryloyloxyethyl isocyanurate,
tripropyleneglycol diacrylate, ethyleneglycol glycerol triacrylate,
glycerol epoxy triacrylate, trimethylolpropane triacrylate,
pentaerythritol triacrylate, pentaerythritol tetraacrylate, and
corresponding methacrylates.
Alternatively, oligomers having radical polymerizable groups can be
used, such as polyester acrylates, urethane acrylates, epoxy
acrylates, and corresponding methacrylates each of which may
include an acryloyl group or methacryloyl group.
More particularly useful radically polymerizable compounds include
those derived from urea urethane (meth)acrylates or urethane
(meth)acrylates having multiple polymerizable groups. For example,
a most preferred radically polymerizable component can be prepared
by reacting DESMODUR.RTM. N100 aliphatic polyisocyanate resin based
on hexamethylene diisocyanate (Bayer Corp., Milford Conn.) with
hydroxyethyl acrylate and pentaerythritol triacrylate. Other
preferred radically polymerizable compounds are available from
Sartomer Company, Inc. such as SR399 (dipentaerythritol
pentaacrylate), SR355 (di-trimethylolpropane tetraacrylate), SR295
(pentaerythritol tetraacrylate), and others that would be readily
apparent to one skilled in the art.
Numerous other radically polymerizable compounds are known to those
skilled in the art and are described in considerable literature
including Photoreactive Polymers: The Science and Technology of
Resists, A Reiser, Wiley, New York, 1989, pp. 102 177, by B. M.
Monroe in Radiation Curing: Science and Technology, S. P. Pappas,
Ed., Plenum, New York, 1992, pp. 399 440, and in "Polymer Imaging"
by A. B. Cohen and P. Walker, in Imaging Processes and Material, J.
M. Sturge et al. Eds., Van Nostrand Reinhold, New York, 1989, pp.
226 262. Useful radically polymerizable components are also
described in EP 1,182,033A1 (noted above), beginning with paragraph
[0170], all of which is incorporated herein by reference.
In some embodiments, the radically polymerizable component
comprises carboxy groups in an amount sufficient to provide an acid
number greater than 0 mg KOH per grams of polymerizable component,
and generally from 0 to about 200 mg KOH per gram of the
polymerizable component. Preferably, the acid number is from 0 to
about 100 mg KOH/gram of polymerizable component and more
preferably, it is from 0 to about 60 mg KOH/gram of polymerizable
component.
Radically polymerizable compounds containing carboxy groups can be
prepared in a number of ways. For example, oligomers containing
carboxy groups can be prepared as described for in the teaching of
Col. 4 (line 42) to Col. 5 (line 19) and Col. 7 (line 14) to Col. 8
(line 45) of U.S. Pat. No. 4,228,232 (Rousseau) that is
incorporated herein by reference. The carboxy groups can be added
to the oligomers preferably after addition of the free radical
polymerizable moieties by reaction of remaining hydroxy groups on
the oligomer backbone with a compound having free carboxy groups
(such as a dicarboxylic acid or anhydride). The resulting oligomers
can be polymerized to provide a desired carboxy-substituted
polymer.
Alternatively, a poly(urea urethane)acrylate or
poly(urethane)acrylate can be prepared from the reaction of a
diisocyanate with a diol having free carboxy groups similarly to
the preparation of allyl functional polyurethanes described in U.S.
Pat. No. 5,919,600 (Huang et al.) that is incorporated by
reference.
The radically polymerizable component is present in the
radiation-sensitive composition in an amount generally sufficient
to render the composition insoluble in an aqueous developer after
exposure to radiation. For example, the weight ratio of radically
polymerizable component to polymeric binder is generally from about
5:95 to about 95:5, preferably from about 10:90 to about 90:10, and
more preferably from about 30:70 to about 70:30. The radically
polymerizable component can be present in an amount of from about
10 to about 70%, preferably from about 20 to about 50%, based on
the totals solids in the radiation sensitive composition, or the
total dry weight of the imageable layer.
The radiation-sensitive composition also includes an initiator
composition that generates radicals sufficient to initiate the
polymerization reaction of the radically polymerizable component(s)
upon imagewise exposure of the composition. The initiator
composition may be useful, for example, in imaging compositions
sensitive to electromagnetic radiation in the ultraviolet, visible
and/or infrared spectral regions, corresponding to the spectral
range of from about 150 to about 1500 nm. Some initiator
compositions can be used at any exposure wavelength while others
are most useful upon exposure within certain regions of the
electromagnetic spectrum.
In general, suitable initiator compositions comprise compounds that
include but are not limited to, amines (such as alkanol amines),
thiol compounds, anilinodiacetic acids or derivatives thereof,
N-phenyl glycine and derivatives thereof, N,N-dialkylaminobenzoic
acid esters, N-arylglycines and derivatives thereof (such as
N-phenylglycine), aromatic sulfonylhalides,
trihalogenomethylsulfones, imides (such as
N-benzoyloxyphthalimide), diazosulfonates, 9,10-dihydroanthracene
derivatives, N-aryl, S-aryl, or O-aryl polycarboxylic acids with at
least 2 carboxy groups of which at least one is bonded to the
nitrogen, oxygen, or sulfur atom of the aryl moiety (such as
aniline diacetic acid and derivatives thereof and other
"co-initiators" described in U.S. Pat. No. 5,629,354 of West et
al.), 1,3,5-triazine derivatives with 1 to 3 --CX.sub.3 groups
wherein X independently represent chlorine or bromine atoms [such
as 2-phenyl-4,6-bis(trichloromethyl)-s-triazine,
2,4,6-tris(trichloromethyl)-s-triazine,
2-methyl-4,6-bis(trichloromethyl)-s-triazine,
2-(styryl-4,6-bis(trichloromethyl)-s-triazine,
2-(p-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine,
2-(4-methoxy-naphtho-1-yl)-4,6-bis(trichloromethyl)-s-triazine,
2-(4-ethoxynaphtho-1-yl)-4,6-bis(trichloromethyl)-s-triazine, and
2-(4-(2-ethoxyethyl)-naphtho-1-yl)-4,6-bis(trichloromethyl)-s-triazine],
oxime ethers and oxime esters (such as those derived from benzoin),
.alpha.-hydroxy or .alpha.-amino-acetophenones,
alkyltriarylborates, trihalogenomethylarylsulfones, benzoin ethers
and esters, peroxides (such as benzoyl peroxide), hydroperoxides
(such as cumyl hydroperoxide), azo compounds (such as azo
bis-isobutyronitrile), 2,4,5-triarylimidazolyl dimers (also known
as hexaarylbisimidazoles, or "HABI's") as described for example in
U.S. Pat. No. 4,565,769 (Dueber et al.), trihalomethyl triazines in
combination with a photosensitizer as described in U.S. Pat. No.
4,997,745 (Kawamura et al.), 3-ketocoumarins for UV and visible
light activation, borate and organoborate salts such as those
described in U.S. Pat. No. 6,562,543 (Ogata et al.), and onium
salts (such as ammonium salts, diaryliodonium salts,
triarylsulfonium salts, aryldiazonium salts, and N-alkoxypyridinium
salts). Other known initiator composition components are described
for example in U.S Patent Application Publication 2003/0064318
(noted above), incorporated herein by reference. Particularly
useful initiator composition components for UV and visible light
sensitive radiation-sensitive compositions include
hexaarylbisimidazoles such as, for example,
2,2-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-biimidazole. The
triazines noted above can be used with exposure at about any
wavelength including UV and visible radiation exposure.
For IR-sensitive radiation-sensitive compositions, the preferred
initiator compositions comprise an onium salt including but not
limited to, a sulfonium, oxysulfoxonium, oxysulfonium, sulfoxonium,
ammonium, selenonium, arsonium, phosphonium, diazonium, or halonium
salt. Further details of useful onium salts, including
representative examples, are provided in U.S. Patent Application
Publication 2002/0068241 (Oohashi et al.), WO 2004/101280 (Munnelly
et al.), and U.S. Pat. No. 5,086,086 (Brown-Wensley et al.), U.S.
Pat. No. 5,965,319 (Kobayashi), and U.S. Pat. No. 6,051,366
(Baumann et al.), that are all incorporated herein by reference.
For example, suitable phosphonium salts include positive-charged
hypervalent phosphorus atoms with four organic substituents.
Suitable sulfonium salts such as triphenylsulfonium salts include a
positively-charged hypervalent sulfur with three organic
substituents. Suitable diazonium salts possess a positive-charged
azo group (that is --N.dbd.N.sup.+). Suitable ammonium salts
include a positively-charged nitrogen atom such as substituted
quaternary ammonium salts with four organic substituents, and
quaternary nitrogen heterocyclic rings such as N-alkoxypyridinium
salts. Suitable halonium salts include a positively-charged
hypervalent halogen atom with two organic substituents. The onium
salts generally include a suitable number of negatively-charged
counterions such as halides, hexafluorophosphate, thiosulfate,
hexafluoroantimonate, tetrafluoroborate, sulfonates, hydroxide,
perchlorate, n-butyltriphenyl borate, tetraphenyl borate, and
others readily apparent to one skilled in the art.
The halonium salts are more preferred, and the iodonium salts are
most preferred. In one preferred embodiment, the onium salt has a
positively-charged iodonium,
(4-methylphenyl)[4-(2-methylpropyl)phenyl]-moiety and a suitable
negatively charged counterion. A representative example of such an
iodonium salt is available as Irgacure.RTM. 250 from Ciba Specialty
Chemicals (Tarrytown, N.Y.) that is
(4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium
hexafluorophosphate and is supplied in a 75% propylene carbonate
solution.
The free radical generating compounds in the initiator composition
are generally present in the radiation-sensitive composition in an
amount of at from about 0.5% to about 30%, and preferably from
about 1 to about 15%, based on composition total solids or total
dry weight of the imageable layer. The optimum amount of the
various sensitizers may differ for various compounds and the
sensitivity of the radiation-sensitive composition that is desired
and would be readily apparent to one skilled in the art.
The radiation-sensitive composition includes one or more
sensitizers that sensitize the composition to radiation having a
.lamda..sub.max of from the UV to the IR region of the
electromagnetic spectrum, that is, from 150 to 1500 nm. Some
sensitizers can be used at any wavelength, but most sensitizers are
optimally useful within certain wavelength ranges. For example,
some sensitizers are optimal for use at an exposure wavelength of
from about 150 to 650 nm (UV to visible) while others are optimal
for use at an exposure wavelength of from about 650 to about 1500
nm (near IR and IR).
In some preferred embodiments, the radiation-sensitive composition
contains a UV sensitizer where the free-radical generating compound
is UV radiation sensitive (that is from about 150 to about 450 nm),
thereby facilitating photopolymerization. Typical UV
radiation-sensitive free-radical generating compounds include
ketocoumarins (particularly in combination with a polycarboxylic
acid free radical generating compound, such as anilino-N,N-diacetic
acid as a secondary co-initiator), trichloromethyl triazines as
described, for example, in U.S. Pat. No. 4,997,745 (Kawamura et
al.) and diaryliodonium salts. Secondary co-initiators can be used,
such as titanocenes, polycarboxylic acids, haloalkyl triazines,
hexaaryl bisimidizoles, borate salts, and photooxidants containing
a heterocyclic nitrogen that is substituted by an alkoxy or acyloxy
group, as described in U.S. Pat. No. 5,942,372 (West et al.).
Sensitizers that absorb in the visible region of the
electromagnetic spectrum (that is from about 400 to about 650 nm)
can also be used. Examples of such sensitizers are well known in
the art and include the compounds described in Cols. 17 22 of U.S.
Pat. No. 6,569,603 (noted above) that is incorporated herein by
reference.
Other useful visible and UV-sensitive sensitizing compositions
include a cyanine dye, diaryliodonium salt, and a co-initiator (as
described above) as described in U.S. Pat. No. 5,368,990 (Kawabata
et al.).
In more preferred embodiments, the radiation sensitive compositions
are sensitized to "violet" radiation in the range of from about 375
to about 450 nm. Useful sensitizers for such compositions include
certain pyrilium and thiopyrilium dyes.
Other useful sensitizers for the violet/visible region of
sensitization are the 2,4,5-triaryloxazole derivatives as described
in WO 2004/074930 (Baumann et al.) that is incorporated herein by
reference. These compounds can be used alone or with a co-initiator
as described above, and especially with the 1,3,5-triazines
described above. Useful 2,4,5-triaryloxazole derivatives can be
represented by the Structure G-(Ar.sub.1).sub.3 wherein Ar.sub.1 is
the same or different, substituted or unsubstituted carbocyclic
aryl group having 6 to 12 carbon atoms in the ring, and G is a
furan, oxazole, or oxadiazole ring. The Ar.sub.1 groups can be
substituted with one or more halo, substituted or unsubstituted
alkyl, substituted or unsubstituted cycloalkyl, substituted or
unsubstituted aryl, amino (primary, secondary, or tertiary), or
substituted or unsubstituted alkoxy or aryloxy groups. Thus, the
aryl groups can be substituted with one or more R'.sub.1 through
R'.sub.3 groups, respectively, that are independently hydrogen or a
substituted or unsubstituted alkyl group having from 1 to 20 carbon
atoms (such as methyl, ethyl, iso-propyl, n-hexyl, benzyl, and
methoxymethyl groups) substituted or unsubstituted carbocyclic aryl
group having 6 to 10 carbon atoms in the ring (such as phenyl,
naphthyl, 4-methoxyphenyl, and 3-methylphenyl groups), substituted
or unsubstituted cycloalkyl group having 5 to 10 carbon atoms in
the ring, a --N(R'.sub.4)(R'.sub.5) group, or a --OR'.sub.6 group
wherein R'.sub.4 through R'.sub.6 independently represent
substituted or unsubstituted alkyl or aryl groups as defined above.
Preferably, at least one of R'.sub.1 through R'.sub.3 is an
--N(R'.sub.4)(R'.sub.5) group wherein R'.sub.4 and R'.sub.5 are the
same or different alkyl groups. Preferred substituents for each
Ar.sub.1 group include the same or different primary, secondary,
and tertiary amines and more preferably they are the same
dialkylamines.
Still another class of useful violet/visible radiation sensitizers
include compounds represented by the Structure Ar.sub.1-G-Ar.sub.2
wherein Ar.sub.1 and Ar.sub.2 are the same or different substituted
or unsubstituted aryl groups having 6 to 12 carbon atoms in the
ring, or Ar.sub.2 can be an arylene-G-Ar.sub.1 or
arylene-G-Ar.sub.2 group, and G is a furan, ozazole, or oxadiazole
ring. Ar.sub.1 is the same as defined above, and Ar.sub.2 can be
the same or different aryl group as Ar.sub.1. "Arylene" can be any
of the aryl groups defined for Ar.sub.1 but with a hydrogen atom
removed to render them divalent in nature.
Additional useful violet-visible radiation sensitizers are the
compounds described in WO 2004/074929 (Baumann et al.) that is also
incorporated herein by reference. These compounds comprise the same
or different aromatic heterocyclic groups connected with a spacer
moiety that comprises at least one carbon--carbon double bond that
is conjugated to the aromatic heterocyclic groups, and are
represented in more detail by Formula (I) of the noted
publication.
In embodiments of the invention that are sensitive to infrared
radiation, the radiation-sensitive compositions can further
comprise an infrared radiation absorbing compound ("IR absorbing
compounds") that absorbs radiation from about 700 to about 1500 nm
and preferably from about 750 to about 1200 nm. It is particularly
useful for such IR absorbing compounds to be used in combination
with onium salts to enhance polymerization of the polymerizable
component and to produce a more durable printing plate.
Examples of suitable IR dyes include but are not limited to, azo
dyes, squarilium dyes, croconate dyes, triarylamine dyes,
thioazolium dyes, indolium dyes, oxonol dyes, oxaxolium dyes,
cyanine dyes, merocyanine dyes, phthalocyanine dyes, indocyanine
dyes, indotricarbocyanine dyes, oxatricarbocyanine dyes,
thiocyanine dyes, thiatricarbocyanine dyes, merocyanine dyes,
cryptocyanine dyes, naphthalocyanine dyes, polyaniline dyes,
polypyrrole dyes, polythiophene dyes, chalcogenopyryloarylidene and
bi(chalcogenopyrylo) polymethine dyes, oxyindolizine dyes, pyrylium
dyes, pyrazoline azo dyes, oxazine dyes, naphthoquinone dyes,
anthraquinone dyes, quinoneimine dyes, methine dyes, arylmethine
dyes, squarine dyes, oxazole dyes, croconine dyes, porphyrin dyes,
and any substituted or ionic form of the preceding dye classes.
Suitable dyes are also described in U.S. Pat. No. 6,569,603 (noted
above, see Cols. 22 28) and U.S. Pat. No. 5,208,135 (Patel et al.)
that are incorporated herein by reference.
Cyanine dyes having an anionic chromophore are also useful in the
present invention. For example, the cyanine dye may have a
chromophore having two heterocyclic groups. In another embodiment,
the cyanine dye may have at least two sulfonic acid groups, more
particularly two sulfonic acid groups and two indolenine groups.
Useful IR-sensitive cyanine dyes of this type are especially useful
for on-press developable radiation-sensitive compositions and
imageable elements as described for example in U.S Patent
Application Publication 2005-0130059 (Tao).
Cyanine dyes may also be useful in combination with a trihalomethyl
triazine and an organoboron salt as described for example in U.S.
Pat. No. 5,496,903 (Watanabe et al.).
A general description of one class of suitable cyanine dyes is
shown by the formula in paragraph 0026 of WO 2004/101280,
incorporated herein by reference, and two specific examples of
useful IR absorbing compounds are identified below with the
Examples as IR Absorbing Dyes I and II.
In addition to low molecular weight IR-absorbing dyes, IR dye
moieties bonded to polymers can be used as well. Moreover, IR dye
cations can be used as well, that is, the cation is the IR
absorbing portion of the dye salt that ionically interacts with a
polymer comprising carboxy, sulfo, phospho, or phosphono groups in
the side chains.
Near infrared absorbing cyanine dyes are also useful and are
described for example in U.S. Pat. No. 6,309,792 (Hauck et al.),
U.S. Pat. No. 6,264,920 (Achilefu et al.), U.S. Pat. No. 6,153,356
(Urano et al.), U.S. Pat. No. 5,496,903 (Watanate et al.). Suitable
dyes may be formed using conventional methods and starting
materials or obtained from various commercial sources including
American Dye Source (Baie D'Urfe, Quebec, Canada) and FEW Chemicals
(Germany). Other useful dyes for near infrared diode laser beams
are described, for example, in U.S. Pat. No. 4,973,572
(DeBoer).
Useful IR absorbing compounds include carbon blacks including
carbon blacks that are surface-functionalized with solubilizing
groups are well known in the art. Carbon blacks that are grafted to
hydrophilic, nonionic polymers, such as FX-GE-003 (manufactured by
Nippon Shokubai), or which are surface-functionalized with anionic
groups, such as CAB-O-JET.RTM. 200 or CAB-O-JET.RTM. 300
(manufactured by the Cabot Corporation) are also useful.
The amount of sensitizer in the radiation-sensitive composition can
vary depending upon the type of compound, exposure wavelength, and
free-radical generating compounds used. Generally, the amount of
sensitizer is from about 1 to about 20% based on the total
composition solid weight or the dry weight coverage of the
imageable element layer in which it is located. For the UV and
visible sensitizers, the preferred amount may be from about 1 to
about 20%, and for the IR and near-IR sensitizers, the coverage may
be from about 1 to about 20%, both based on total composition solid
weight or dry layer weight.
The polymeric binders useful in the present invention comprise a
polymer backbone and have attached thereto a carbazole derivative
represented by the following Structure (I):
##STR00003## wherein Y is a direct bond or a divalent linking
group. Such linking groups can include, but are not limited to,
substituted or unsubstituted alkylene groups having 1 to 4 carbon
atoms, substituted or unsubstituted phenylene groups, oxy, thio,
--NR'-- (wherein R' is hydrogen or an alkyl group), --C(O)--,
--C(O)O--, --S(O).sub.2--, or combinations of two or more of such
groups.
R.sup.1 to R.sup.8 are independently hydrogen, or a substituted or
unsubstituted alkyl group having 1 to 8 carbon atoms (such as
methyl, ethyl, iso-propyl, n-pentyl, benzyl, and iso-octyl groups),
substituted or unsubstituted alkenyl groups having 2 to 4 carbon
atoms (such as ethenyl, allyl, or propenyl groups), substituted or
unsubstituted aryl groups having 6 to 10 carbon atoms in the
aromatic ring (such as phenyl, 4-methylphenyl, and naphthyl), halo
groups (such as chloro or bromo), cyano, substituted or
unsubstituted alkoxy groups having 1 to 8 carbon atoms (such as
methoxy, ethoxy, 2-propoxy, and n-octyloxy), substituted or
unsubstituted acyl or acyloxy groups, or a carboxylate group.
Alternatively, any adjacent R.sup.1 through R.sup.8 groups can
together form a substituted or unsubstituted carbocyclic or
heterocyclic group or a fused aromatic ring.
Preferably, Y is direct bond, and R.sup.1 to R.sup.8 are
independently hydrogen, or alkyl groups having 1 to 8 carbon atoms
or halo groups. More preferably, each of R.sup.1 to R.sup.8 is
hydrogen.
The polymeric binder generally has an acid value of from about 5 to
about 400 mg KOH/g (preferably from about 10 to about 200, and more
preferably from about 30 to about 150, mg KOH/g), and can also be
represented by the following Structure (II):
##STR00004## wherein A represents recurring units comprising the
carbazole derivative represented by Structure (I), B represents
recurring units derived from ethylenically unsaturated
polymerizable monomers that do not comprise a carbazole derivative,
x is from about 0.1 to about 99.9 mol % (preferably from about 5 to
about 50 mol %), and y is from about 0.1 to about 99.9 mol %
(preferably from about 50 to about 95 mol %), based on total
recurring units.
In Structure (II), B represents recurring units derived from one or
more ethylenically unsaturated polymerizable monomers that do not
have a pendant carbazole group (or derivative thereof). A variety
of monomers can be used for providing B recurring units, including
styrenic monomers, (meth)acrylamide, (meth)acrylates, (meth)acrylic
acids, (meth)acrylonitrile, vinyl acetate, maleic anhydride,
N-substituted maleimide, or mixtures thereof. However, more
particularly useful monomers are represented by the following
Structures (III) through (VII):
##STR00005## wherein R.sup.9 and R.sup.10 are independently
hydrogen, substituted or unsubstituted alkyl groups having 1 to 6
carbon atoms, substituted or unsubstituted alkenyl groups having 1
to 6 carbon atoms, substituted or unsubstituted aryl groups
(including aromatic carbocyclic and heterocyclic groups), halo
groups, substituted or unsubstituted alkoxy groups having 1 to 6
carbon atoms, substituted or unsubstituted acyl groups having 1 to
6 carbon atoms, substituted or unsubstituted acyloxy groups having
1 to 6 carbon atoms, or R.sup.9 and R.sup.10 together can form a
cyclic group, such as a cyclopentyl or cyclohexyl group or form one
of the following divalent groups:
--NHC(O)CH.sub.2CH.sub.2CH.sub.2--, --NHC(O)CH.sub.2CH.sub.2--,
--CH.sub.2C(O)OC(O)--, --(CH.sub.2).sub.2C(O)OC(O)--, and
--CH.sub.2C(O)OC(O)CH.sub.2--. R.sup.9 and R.sup.10 are preferably
hydrogen or methyl.
R.sup.11 is hydrogen or a substituted or unsubstituted alkyl group
having 1 to 6 carbon atoms, substituted or unsubstituted aryl group
(including aromatic carbocyclic and heterocyclic groups), or halo
group. R.sup.11 is preferably hydrogen or methyl.
R.sup.12 is hydrogen or a substituted or unsubstituted alkyl group
having 1 to 6 carbon atoms, substituted or unsubstituted aryl group
(both aromatic carbocyclic or heterocyclic groups), cyano group, or
halo group. R.sup.12 is preferably a substituted or unsubstituted
phenyl group (that is, to provide a styrenic monomer).
R.sup.13 is hydrogen or a substituted or unsubstituted alkyl group
having 1 to 20 carbon atoms, substituted or unsubstituted alkenyl
group having 1 to 20 carbon atoms, substituted or unsubstituted
cycloalkyl group, substituted or unsubstituted cycloalkenyl group,
substituted or unsubstituted aryl group (including aromatic
carbocyclic and heterocyclic groups), or substituted or
unsubstituted alkoxyalkylene group having 1 to 20 carbon atoms.
R.sup.13 is preferably methyl, ethyl, or hydroxyethyl.
R.sup.14 and R.sup.15 are independently hydrogen or substituted or
unsubstituted alkyl groups having 1 to 20 carbon atoms, substituted
or unsubstituted alkenyl groups having 1 to 20 carbon atoms,
substituted or unsubstituted cycloalkyl groups, substituted or
unsubstituted cycloalkenyl groups, substituted or unsubstituted
aryl groups (including aromatic carbocyclic and heterocyclic
groups), or substituted or unsubstituted alkoxyalkylene groups
having 1 to 12 carbon atoms. R.sup.14 and R.sup.15 are preferably
independently hydrogen or methyl.
R.sup.16 and R.sup.17 are independently hydrogen or substituted or
unsubstituted alkyl groups having 1 to 6 carbon atoms, substituted
or unsubstituted alkenyl groups having 1 to 6 carbon atoms,
substituted or unsubstituted aryl groups (including carbocyclic and
heterocyclic groups), halo groups, cyano groups, substituted or
unsubstituted alkoxy groups having 1 to 6 carbon atoms, substituted
or unsubstituted acyl groups having 1 to 6 carbon atoms, or
substituted or unsubstituted acyloxy groups having 1 to 6 carbon
atoms. R.sup.16 and R.sup.17 are independently preferably hydrogen,
methyl, or phenyl.
R.sup.18 is hydrogen or a substituted or unsubstituted alkyl group
having 1 to 7 carbon atoms (including a benzyl group), substituted
or unsubstituted aryl group (including aromatic carbocyclic and
heterocyclic groups), or hydroxy group. R.sup.18 is generally
hydrogen or a substituted or unsubstituted phenyl group.
Preferably, the recurring units represented by B are derived from
styrene, N-phenylmaleimide, (meth)acrylic acid,
(meth)acrylonitrile, 2-hydroxyethyl methacrylate, or methyl
methacrylate, or mixtures of two or more of these monomers.
The polymeric binder is present in the radiation-sensitive
composition in an amount sufficient to render the
radiation-sensitive composition soluble or dispersible in an
aqueous developer. Generally, this amount is from about 10 to about
90 weight %, preferably from about 20 to about 70 weight % and more
preferably from 30 to 60 weight %.
The polymeric binders useful in this invention are solids and
generally have a glass transition (T.sub.g) temperature of from
about 35 to about 220.degree. C., preferably from about 45 to about
180.degree. C., and more preferably from about 50 to about
130.degree. C., as measured using conventional procedures.
In addition, the polymeric binders generally have a number average
molecular weight (M.sub.n) of from about 1,000 to about 1,000,000
and preferably from about 5,000 to about 100,000.
The polymeric binders containing a carbazole derivative can be
prepared using conventional radical polymerization conditions and
known starting materials. More details about such polymerization
methods are provided by Belfield et al. (Eds.), Photoinitiated
Polymerization. ASC Symposium Series 847, American Chemical
Society, Washington, D.C., 2003, pp. 219 230. Representative
polymerization methods are shown below prior to the Examples.
In addition to the polymeric binders described above, the
radiation-sensitive composition may also include one or more
"co-binders" that do not contain carbazole moieties. However, when
such co-binders are present, they comprise less than 50% based on
the total polymeric binder weight. Useful co-binders include but
are not limited to, cellulosic polymers, poly(vinyl alcohols),
polymers derived from (meth)acrylic acid, poly(vinyl pyrrolidones),
polymers of meth(acrylates), polyesters, polyacetals, and mixtures
thereof. Such co-binders can also provide crosslinkable sites.
The radiation-sensitive composition may further include a
poly(alkylene glycol) or an ether or ester thereof that has a
molecular weight of from about 200 and up to 4000 (preferably from
about 500 to about 2000). This compound may be present in an amount
of from about 2 to about 50 weight % (preferably from about 5 to
about 30%) based on the total solids content of the composition, or
the total dry weight of the imageable layer. Particularly useful
compounds of this type include, but are not limited to, one or more
of polyethylene glycol, polypropylene glycol, polyethylene glycol
methyl ether, polyethylene glycol dimethyl ether, polyethylene
glycol monoethyl ether, polyethylene glycol diacrylate, ethoxylated
bisphenol A di(meth)acrylate, and polyethylene glycol mono
methacrylate. Also useful are SR9036 (ethoxylated (30)bisphenol A
dimethacrylate), CD9038 (ethoxylated (30)bisphenol A diacrylate),
and SR494 (ethoxylated (5)pentaerythritol tetraacrylate), and
similar compounds all of which that can be obtained from Sartomer
Company, Inc.
Other materials that may be present in the radiation-sensitive
composition include a styrene-acrylonitrile-poly(ethylene oxide)
graft copolymer, colorants, viscosity builders, surfactants,
dispersing agents, humectants, biocides, plasticizers, pH
adjusters, drying agents, defoamers, preservatives, antioxidants,
development aids, rheology modifiers or combinations thereof, or
any other addenda commonly used in the lithographic art, in
conventional amounts. Useful viscosity builders include
hydroxypropyl cellulose, hydroxyethyl cellulose, carboxymethyl
cellulose, and poly(vinyl pyrrolidones).
The radiation-sensitive composition may also include a mercaptan
derivative such as a mercaptotriazole such as
3-mercapto-1,2,4-triazole, 4-methyl-3-mercapto-1,2,4-triazole,
5-mercapto-1-phenyl-1,2,4-triazole,
4-amino-3-mercapto-1,2,4,-triazole,
3-mercapto-1,5-diphenyl-1,2,4-triazole, and
5-(p-aminophenyl)-3-mercapto-1,2,4-triazole. Various
mercaptobenzimidazoles, mercaptobenzthiazoles, and
mercaptobenzoxazoles may also be present.
Imageable Elements
The imageable elements are formed by suitable application of a
radiation-sensitive composition as described above to a suitable
substrate. This substrate is usually treated or coated in various
ways as described below prior to application of the
radiation-sensitive composition. Preferably, there is only a single
imageable layer comprising the radiation-sensitive composition of
this invention. If the substrate has been treated to provide an
"interlayer" for improved adhesion or hydrophilicity, the applied
radiation-sensitive composition is considered the "top" layer.
The substrate generally has a hydrophilic surface, or at least a
surface that is more hydrophilic than the applied
radiation-sensitive composition on the imaging side. The substrate
comprises a support that can be composed of any material that is
conventionally used to prepare imageable elements such as
lithographic printing plates. It is usually in the form of a sheet,
film, or foil, and is strong, stable, and flexible and resistant to
dimensional change under conditions of use so that color records
will register a full-color image. Typically, the support can be any
self-supporting material including polymeric films (such as
polyester, polyethylene, polycarbonate, cellulose ester polymer,
and polystyrene films), glass, ceramics, metal sheets or foils, or
stiff papers (including resin-coated and metallized papers), or a
lamination of any of these materials (such as a lamination of an
aluminum foil onto a polyester film). Metal supports include sheets
or foils of aluminum, copper, zinc, titanium, and alloys
thereof.
Polymeric film supports may be modified on one or both surfaces
with a "subbing" layer to enhance hydrophilicity, or paper supports
may be similarly coated to enhance planarity. Examples of subbing
layer materials include but are not limited to, alkoxysilanes,
aminopropyltriethoxysilanes, glycidioxypropyltriethoxysilanes, and
epoxy functional polymers, as well as conventional hydrophilic
subbing materials used in silver halide photographic films (such as
gelatin and other naturally occurring and synthetic hydrophilic
colloids and vinyl polymers including vinylidene chloride
copolymers).
A preferred substrate is composed of an aluminum support that may
be treated using techniques known in the art, including physical
graining, electrochemical graining, chemical graining, and
anodizing. Preferably, the aluminum sheet is anodized using
phosphoric acid or sulfuric acid and conventional procedures.
An interlayer may be formed by treatment of the aluminum support
with, for example, a silicate, dextrine, calcium zirconium
fluoride, hexafluorosilicic acid, phosphate/fluoride, poly(vinyl
phosphonic acid) (PVPA), vinyl phosphonic acid copolymer,
poly(acrylic acid), or acrylic acid copolymer. Preferably, the
aluminum support is treated with poly(acrylic acid) using known
procedures to improve surface hydrophilicity.
Particularly useful imageable elements have substrates that are
phosphoric acid anodized, poly(acrylic acid)-treated aluminum
substrates or sulfuric acid anodized, sodium phosphate/sodium
fluoride-treated aluminum substrates.
The thickness of the substrate can be varied but should be
sufficient to sustain the wear from printing and thin enough to
wrap around a printing form. Preferred embodiments include a
treated aluminum foil having a thickness of from about 100 to about
600 .mu.m.
The backside (non-imaging side) of the substrate may be coated with
antistatic agents and/or slipping layers or a matte layer to
improve handling and "feel" of the imageable element.
The substrate can also be a cylindrical surface having the
radiation-sensitive composition applied thereon, and thus be an
integral part of the printing press. The use of such imaged
cylinders is described for example in U.S. Pat. No. 5,713,287
(Gelbart).
The radiation-sensitive composition can be applied to the substrate
as a solution or dispersion in a coating liquid using any suitable
equipment and procedure, such as spin coating, knife coating,
gravure coating, die coating, slot coating, bar coating, wire rod
coating, roller coating, or extrusion hopper coating. The
composition can also be applied by spraying onto a suitable support
(such as an on-press printing cylinder).
Illustrative of such methods is mixing the polymeric binder and
other components of the radiation-sensitive composition in a
suitable organic solvent [such as methyl ethyl ketone (2-butanone),
methanol, ethanol, iso-propyl alcohol, acetone, n-propanol, and
others readily known in the art, as well as mixtures thereof],
dispersing the resulting solution in an aqueous medium, applying
the resulting dispersion on a substrate, and removing the
solvent(s) by evaporation under suitable drying conditions. After
proper drying, the coating weight of the imageable layer is
generally from about 0.1 to about 5 g/m.sup.2, preferably from
about 0.5 to about 3.5 g/m.sup.2, and more preferably from about
0.5 to about 1.5 g/m.sup.2.
The imageable element may further comprise an oxygen-impermeable
overcoat layer that may serve as an oxygen barrier by comprising an
oxygen-impermeable compound, that is, a compound that prevents the
diffusion of oxygen from the atmosphere into the imageable layer
during the lifetime of the free radicals generated by radiation
exposure. The overcoat can also serve as a barrier to moisture. The
overcoat layer is disposed on the imageable layer and should be
soluble, dispersible, or at least permeable to the developer. The
overcoat layer can also be designed to prevent physical or chemical
damage to the imageable element from handling, transportation, or
overexposure. Further details of such overcoat layers are provided
in WO 99/06890 (Pappas et al.).
Underlayers can also be present under the imageable layer to
enhance developability or to act as a thermal insulating layer. The
underlying layer should be soluble or at least dispersible in the
developer and preferably have a relatively low thermal conductivity
coefficient.
The imageable elements have any useful form including, but not
limited to, printing plate precursors, printing cylinders, printing
sleeves and printing tapes (including flexible printing webs).
Preferably, the imageable members are printing plate
precursors.
Printing plate precursors can be of any useful size and shape (for
example, square or rectangular) having the requisite imageable
layer disposed on a suitable substrate. Printing cylinders and
sleeves are known as rotary printing members having the substrate
and imageable layer in a cylindrical form. Hollow or solid metal
cores can be used as substrates for printing sleeves.
Imaging Conditions
During use, the imageable element is exposed to a suitable source
of radiation such as UV, visible light, or infrared radiation,
depending upon the sensitivity of the radiation-sensitive
composition, at a wavelength of from about 150 to about 1500 nm. As
noted above, in some embodiments, imaging is carried out using an
infrared laser at a wavelength of from about 700 to about 1200 nm,
and in other embodiments, imaging is carried out in the UV or
visible regions of the electromagnetic spectrum, that is from about
150 to about 700 nm. The lasers used to expose the imaging member
of this invention are preferably diode lasers, because of the
reliability and low maintenance of diode laser systems, but other
lasers such as gas or solid-state lasers may also be used. The
combination of power, intensity and exposure time for laser imaging
would be readily apparent to one skilled in the art.
The imaging apparatus can function solely as a platesetter or it
can be incorporated directly into a lithographic printing press. In
the latter case, printing may commence immediately after imaging,
thereby reducing press set-up time considerably. The imaging
apparatus can be configured as a flatbed recorder or as a drum
recorder, with the imageable member mounted to the interior or
exterior cylindrical surface of the drum. Examples of useful
imaging apparatus are available as models of Creo Trendsetter.RTM.
imagesetters available from Creo, a subsidiary of Eastman Kodak
Company (Burnaby, British Columbia, Canada) that contain laser
diodes that emit near infrared radiation at a wavelength of about
830 nm. Other suitable imaging sources include the Crescent 42T
Platesetter that operates at a wavelength of 1064 nm and the Screen
PlateRite 4300 series or 8600 series platesetter (available from
Screen, Chicago, Ill.). Additional useful sources of radiation
include direct imaging presses that can be used to image an element
while it is attached to the printing plate cylinder. An example of
a suitable direct imaging printing press includes the Heidelberg
SM74-DI press (available from Heidelberg, Dayton, Ohio).
Useful "violet" laser imaging apparatus include the Prosetter
platesetter from Heidelberger Druckmaschinene (Heidelburg,
Germany), Mako 8 CTP platesetter from ECRM Imaging Systems
(Tewksbury, Mass.), Polaris platesetter from Agfa Graphics
(Mortsel, Belgium), LaserStar Jet CTP platesetter from Krause CTP
Ltd. (Milford, Conn.), PlateRite 2044Vi platesetter from Screen
Media Technology (Rolling Meadows, Ill.), and Saber Luxel Vx-9600
CTP platesetter from Fuji Photo (Valhalla, N.Y.).
Imaging speeds using infrared radiation imaging may be in the range
of from about 20 to about 1500 mJ/cm.sup.2, and more particularly
from about 75 to about 400 mJ/cm.sup.2. For imaging using
ultraviolet/visible radiation, the imaging speeds may be from about
10 to about 200 .mu.J/cm.sup.2.
While laser imaging is preferred in the practice of this invention,
imaging can be provided by any other means that provides thermal
energy in an imagewise fashion. For example, imaging can be
accomplished using a thermoresistive head (thermal printing head)
in what is known as "thermal printing", described for example in
U.S. Pat. No. 5,488,025 (Martin et al.). Thermal print heads are
commercially available for example, as a Fujitsu Thermal Head
FTP-040 MCS001 and TDK Thermal Head F415 HH7-1089.
The imaged elements can be developed using conventional processing
conditions and a conventional aqueous alkaline developer. The
aqueous developer composition is dependent upon the nature of the
polymeric binder, but common components include surfactants,
chelating agents (such as salts of ethylenediaminetetraacetic
acid), organic solvents (such as benzyl alcohol), and alkaline
components (such as inorganic metasilicates, organic metasilicates,
hydroxides, and bicarbonates). The pH of the aqueous developer is
preferably from about 5 to about 14.
Aqueous alkaline developers generally have a pH of at least 7 and
preferably of at least 11. The higher pH developers are generally
best for processing the single-layer elements. Useful alkaline
aqueous developers include 3000 Developer, 9000 Developer, GOLDSTAR
Developer, GREENSTAR Developer, ThermalPro Developer, PROTHERM
Developer, MX1813 Developer, and MX1710 Developer (all available
from Kodak Polychrome Graphics, a subsidiary of Eastman Kodak
Company). These compositions also generally include surfactants,
chelating agents (such as salts of ethylenediaminetetraacetic
acid), and alkaline components (such as inorganic metasilicates,
organic metasilicates, hydroxides, and bicarbonates).
Solvent-based alkaline developers are generally single-phase
solutions of one or more organic solvents that are miscible with
water. Useful organic solvents include the reaction products of
phenol with ethylene oxide and propylene oxide [such as ethylene
glycol phenyl ether (phenoxyethanol)], benzyl alcohol, esters of
ethylene glycol and of propylene glycol with acids having 6 or less
carbon atoms, and ethers of ethylene glycol, diethylene glycol, and
of propylene glycol with alkyl groups having 6 or less carbon
atoms, such as 2-ethylethanol and 2-butoxyethanol. The organic
solvent(s) is generally present in an amount of from about 0.5 to
about 15% based on total developer weight.
Representative solvent-based alkaline developers include ND-1
Developer, 955 Developer, Developer 980, and 956 Developer
(available from Kodak Polychrome Graphics a subsidiary of Eastman
Kodak Company).
Developers T-190-4 and T-190-11 may be preferred for
radiation-sensitive compositions that are imaged using "violet"
light. These developers can be obtained from Kodak Polychrome
Graphics, a subsidiary of Eastman Kodak Company.
Generally, the alkaline developer is applied to the imaged element
by rubbing or wiping the outer layer with an applicator containing
the developer. Alternatively, the imaged element can be brushed
with the developer or the developer may be applied by spraying the
outer layer with sufficient force to remove the exposed regions.
Still again, the imaged element can be immersed in the developer.
In all instances, a developed image is produced in a lithographic
printing plate having excellent resistance to press room
chemicals.
Following development, the imaged element can be rinsed with water
and dried in a suitable fashion. The dried element can also be
treated with a conventional gumming solution (preferably gum
arabic). In addition, a postbake operation can be carried out.
Printing can be carried out by applying a lithographic ink and
fountain solution to the printing surface of the imaged element.
The fountain solution is taken up by the non-imaged regions on the
surface of the hydrophilic substrate revealed by the imaging and
development steps, and the ink is taken up by the imaged
(non-removed) regions on the imaged layer. The ink is then
transferred to a suitable receiving material (such as cloth, paper,
metal, glass, or plastic) to provide a desired impression of the
image thereon. If desired, an intermediate "blanket" roller can be
used to transfer the ink from the imaged member to the receiving
material. The imaged members can be cleaned between impressions, if
desired, using conventional cleaning means.
The following examples are provided to illustrate the practice of
the invention but are by no means intended to limit the invention
in any manner.
EXAMPLES
The components and materials used in the examples and analytical
were as follows:
Polymer H is a copolymer derived from 13 mol % methacrylic acid and
87 mol % methyl methacrylate.
Oligomer A is a urethane acrylate prepared by reacting
Desmodur.RTM. N 100 with hydroxyethyl acrylate and pentaerythritol
triacrylate (80 wt. % in MEK).
Oligomer B is a urethane acrylate prepared by reacting 2 parts of
hexamethylene diisocyanate with 2 parts of hydroxyethyl
methacrylate and 1 part of 2-(2-hydroxyethyl)piperidine.
PMI is N-phenylmaleimide.
Kayamer PM-2 is a mixture of mono- and di-esters of phosphoric acid
with 2-hydroxyethyl methacrylate and was obtained from Nippon
Kayaku (Tokyo, Japan).
NK Ester BPE-500 is
2,2-bis[4-(methacryloxypolyethoxy)-phenylpropane that was obtained
from Shin-Nakamura Chemical Co. (Wakayama City, Japan).
Initiator A is 4-methylphenyl-4'-isobutylphenyl iodonium
tetraphenylborate that was obtained from Ciba Specialty
Chemicals.
o-Cl--HABI is
2,2-bis-(-2-chlorophenyl)-4,4',5,5'-tetraphenyl-biimidazole that
was obtained from Hampford Research Inc. (Stratford, Conn.).
IRT is an IR dye available from Showa Denko, Tokyo, Japan.
IR Dye 1 has the following structure:
##STR00006##
UV Dye 2 was obtained from Clariant (Frankfort, Germany) and has
the following structure:
##STR00007##
Pigment A (951) is a 27% solids dispersion of 7.7 parts of a
polyvinyl acetal derived from polyvinyl alcohol acetalized with
acetaldehyde, butyraldehyde and 4-formylbenzoic acid, 76.9 parts of
Irgalith Blue GLVO (Cu-phthalocyanaine C.I. Pigment Blue 15:4), and
15.4 parts of Disperbyk.RTM. 167 dispersing aid (from Byk Chemie)
in 1-methoxy-2-propanol.
Byk.RTM. 307 is a dispersion of polyethoxylated
dimethylpolysiloxane co-polymer (Byk Chemie, Wallingford, Conn.,
USA).
956 Developer is an alkaline developer that is commercially
available from Kodak Polychrome Graphics (Norwalk, Conn.), a
subsidiary of Eastman Kodak Company.
ND-1 developer is an alkaline developer that is commercially
available from Kodak Polychrome Graphics, Japan, a subsidiary of
Eastman Kodak Company.
T190-4 developer is an alkaline developer that is commercially
available from Kodak Polychrome Graphics (Norwalk, Conn.), a
subsidiary of Eastman Kodak Company.
T190-11 developer is an alkaline developer that is commercially
available from Kodak Polychrome Graphics, Inc. (Norwalk,
Conn.).
PGME is 1-methoxy-2-propanol.
MEK is methyl ethyl ketone.
BLO is .gamma.-butyrolactone.
The following polymeric binders were prepared and used in the
Examples below:
Synthesis of Polymer A (Invention):
Azobis(isobutyronitrile) (AIBN, 0.4 g), methyl methacrylate (5 g),
acrylonitrile (9 g), N-vinyl carbazole (5 g), methacrylic acid (2
g), and N,N-dimethylacetamide (80 g) were placed in a 500-ml
3-necked flask, equipped with magnetic stirring, temperature
controller, and N.sub.2 inlet. The mixture was heated to 60.degree.
C. and stirred under N.sub.2 protection overnight (.about.16 hours)
to provide about 20% solids. The reaction mixture was then slowly
dropped into 3 liters of ice water while stirring. The resulting
precipitate was filtered and washed with 250 ml of n-propanol, and
dried in an oven at 50.degree. C. for 3 hours to provide 18.4 g of
white solid.
Synthesis of Polymer B (Invention):
AIBN (0.4 g), methyl methacrylate (4 g), acrylonitrile (9 g),
N-vinyl carbazole (5 g), methacrylic acid (2 g), and
N,N-dimethylacetamide (80 g) were placed in a 500-ml 3-necked
flask, equipped with magnetic stirring, temperature controller and
N.sub.2 inlet. The mixture was heated to 60.degree. C. and stirred
under N.sub.2 protection overnight (.about.16 hours) to provide
about 20% solids. The reaction mixture was then slowly dropped into
3 liters of ice water while stirring. The resulting precipitate was
filtered and washed with 250 ml of n-propanol, and dried in an oven
at 50.degree. C. for 3 hours to provide 18.0 g of white solid.
Synthesis of Polymer C (Comparative):
AIBN (0.4 g), methyl methacrylate (4 g), acrylonitrile (9 g), PMI
(5 g), methacrylic acid (2 g), and N,N-dimethylacetamide (80 g)
were placed in a 500-ml 3-necked flask, equipped with magnetic
stirring, temperature controller, and N.sub.2 inlet. The mixture
was heated to 60.degree. C. and stirred under N.sub.2 protection
overnight (.about.16 hours) to provide 18.6% solids. The reaction
mixture was then slowly dropped into 3 liters of ice water while
stirring. The resulting precipitate was filtered and washed with
250 ml of n-propanol, and dried in an oven at 50.degree. C. for 3
hours to provide 15.5 g of white solid.
Synthesis of Polymer D (Comparative):
AIBN (0.4 g), methyl methacrylate (4 g), acrylonitrile (9 g),
styrene (4 g), methacrylic acid (2 g), and N,N-dimethylacetamide
(80 g) were placed in a 500-ml 3-necked flask, equipped with
magnetic stirring, temperature controller, and N.sub.2 inlet. The
mixture was heated to 60.degree. C. and stirred under N.sub.2
protection overnight (.about.16 hours) to provide 19.3% solids. The
reaction mixture was then slowly dropped into 3 liters of ice water
while stirring. The resulting precipitate was filtered and washed
with 250 ml of n-propanol, and dried in an oven at 50.degree. C.
for 3 hours to provide 18.5 g of white solid.
Synthesis of Polymer E (Comparative):
AIBN (0.4 g), methyl methacrylate (9 g), acrylonitrile (9 g),
methacrylic acid (2 g), and N,N-dimethylacetamide (80 g) were
placed in a 500-ml 3-necked flask, equipped with magnetic stirring,
temperature controller, and N.sub.2 inlet. The mixture was heated
to 60.degree. C. and stirred under N.sub.2 protection overnight
(.about.16 hours) to provide 19.2% solids. The reaction mixture was
then slowly dropped into 3 liters of ice water while stirring. The
resulting precipitate was filtered and washed with 250 ml of
n-propanol, and dried in an oven at 50.degree. C. for 3 hours to
provide 17.0 g of white solid.
Synthesis of Polymer F (Invention):
AIBN (0.4 g), methyl methacrylate (2 g), N-vinyl carbazole (7 g),
acrylonitrile (9 g), methacrylic acid (2 g), and
N,N-dimethylacetamide (80 g) were placed in a 500-ml 3-necked
flask, equipped with magnetic stirring, temperature controller, and
N.sub.2 inlet. The mixture was heated to 60.degree. C. and stirred
under N.sub.2 protection overnight (.about.16 hours) to provide
about 20% solids. The reaction mixture was then slowly dropped into
3 liters of ice water while stirring. The resulting precipitate was
filtered and washed with 250 ml of n-propanol, and dried in an oven
at 50.degree. C. for 3 hours to provide 19.0 g of white solid.
Synthesis of Polymer G (Invention):
AIBN (0.4 g), 2-hydroxyethyl methacrylate (2 g), acrylonitrile (7
g), styrene (4 g), N-vinyl carbazole (5 g), methacrylic acid (2 g),
and N,N-dimethylacetamide (80 g) were placed in a 500-ml 3-necked
flask, equipped with magnetic stirring, temperature controller, and
N.sub.2 inlet. The mixture was heated to 60.degree. C. and stirred
under N.sub.2 protection overnight (.about.16 hours) to provide
about 20% solids. The reaction mixture was then slowly dropped into
3 liters of ice water while stirring. The resulting precipitate was
filtered and washed with 250 ml of n-propanol, and dried in an oven
at 50.degree. C. for 3 hours to provide 17.7 g of white solid.
Invention Examples 1 4 and Comparative Examples 1 3
IR-sensitive imageable layer coating formulations were prepared by
dissolving 0.98 g of Invention polymers A, B, F, and G (for
Examples 1 4, respectively) or Comparative polymers C, D, and E
(Comparative Examples 1 3, respectively), Oligomer A (0.91 g),
Initiator A (0.22 g), IRT (0.09 g), 3-mercaptotriazole (0.05 g),
Pigment A (0.30 g), polyethylene glycol methyl ether (0.54 g,
MW=750, Aldrich), and 10% Byk.RTM. 307 (0.27 g) in PGME (25.8 g),
MEK (16.2 g), and BLO (4.7 g). A mechanically-grained and
phosphoric acid anodized aluminum substrate that had been
post-treated with poly(acrylic acid) was coated with each coating
formulation to provide a dry coating weight of about 1.3 g/m.sup.2
in the imageable layer when properly dried at 170.degree. F.
(77.degree. C.) for about 2 minutes on a rotating drum.
The resulting imageable elements of Invention Examples 1 4 and
Comparative Examples 1 3 were imaged on a CREO Trendsetter 3244x
image setter (Creo, a subsidiary of Eastman Kodak Company, Burnaby,
British Columbia, Canada) using an 830 nm IR laser in the range
from 40 to 210 mJ/cm.sup.2. Each imaged element was then developed
using an Anitec Duplex 16 processor charged with ND-1 developer at
25.degree. C. to provide imaged printing plates.
The optical densities of the resulting images as a function of
exposure energy are shown in FIG. 1. The results show that use of
the carbazole-containing Polymers A, B, F, and G in Examples 1 4
provided higher optical density in the image area than use of the
Comparative Polymers C, D, and E in Comparative Example 1 3,
suggesting that the polymerization efficiency was improved with use
of the carbazole-containing polymers according to the present
invention.
Invention Example 5
An IR-sensitive imageable layer coating formulation (composition of
the present invention) was prepared by dissolving Polymer A (2.5
g), Oligomer A (2.34 g), Initiator A (0.57 g), IRT (0.21 g),
3-mercaptotriazole (0.13 g), Pigment A (0.76 g), polyethylene
glycol methyl ether (1.36 g, MW=750, Aldrich), and 10% Byk.RTM. 307
(0.69 g) in PGME (45.9 g), MEK (40.9 g), and BLO (4.7 g). A
mechanically-grained and phosphoric acid anodized aluminum
substrate that had been post-treated with poly(acrylic acid) was
coated with the coating formulation to provide an imageable layer
having a dry coating weight of about 1.3 g/m.sup.2 when properly
dried at 170.degree. F. (77.degree. C.) for about 2 minutes on a
rotating drum.
The resulting imageable element was placed on a CREO Trendsetter
3244x imagesetter and exposed to an 830 nm IR laser at about 120
mJ/cm.sup.2. The imaged element was then developed using an Anitec
Duplex 16 processor charged with ND-1 developer at 25.degree. C.
The resulting imaged printing plate was mounted on a Miehle
sheet-fed press using ink containing 1.5% calcium carbonate to
produce at least 10,000 good impressions.
Invention Example 6
An IR-sensitive imageable layer coating formulation (composition of
the present invention) was prepared by dissolving Polymer B (2.71
g), Oligomer A (3.21 g), Sartomer 355 (0.54 g, ditrimethylolpropane
tetraacrylate, Sartomer Co., Inc.),
2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-2-triazine (0.32 g),
N-phenyliminodiacetic acid (0.17 g), IR Dye 1 (0.11 g), crystal
violet (0.08 g), and 10% Byk.RTM. 307 (0.14 g) in PGME (50.4 g),
MEK (36.7 g), and BLO (4.7 g). An electrochemically grained and
anodized aluminum substrate, post-treated with sodium
phosphate/sodium fluoride, was coated with coating formulation to
provide an imageable layer having a dry coating weight of about 1.2
g/m.sup.2 when properly dried at 170.degree. F. (77.degree. C.) for
about 2 minutes on a rotating drum.
An overcoat formulation was prepared by mixing 9.7% Airvol 203
(67.9 g, polyvinyl alcohol), 20% poly(vinyl imidazole) (5.83 g),
2-propanol (20.7 g), and deionized water (405.6 g). After applying
the overcoat formulation over the imageable layer, the element was
dried at 170.degree. F. (77.degree. C.) for about 1 minute on a
rotating drum to yield a dry coating weight about 0.5
g/m.sup.2.
The resulting imageable element was placed on a CREO Trendsetter
3244x imagesetter and exposed to an 830 nm IR laser in the range of
from 20 to 120 mJ/cm.sup.2. The imaged element was then developed
by hand with diluted 956 Developer at 25.degree. C. The minimum
exposure energy to achieve maximum processed density was about 40
mJ/cm.sup.2. This image printing plate passed a 5-day keeping test
at 50.degree. C., but it lost the image during a 5-day keeping test
at 38.degree. C. and 80% humidity.
Invention Example 7 and Comparative Example 4
UV-sensitive imageable layer formulations were prepared with the
components shown in TABLE I:
TABLE-US-00001 TABLE 1 Inventive Example 7 Comparative Example 4
(parts by weight) (parts by weight) Polymer A 1.50 -- Polymer H --
1.50 NK Ester BPE 500 0.50 0.50 Oligomer B 2.73 2.74 Kayamer PM-2
0.07 0.07 UV Dye 2 0.93 0.93 o-Cl-HABI 0.23 0.23 3-Mercaptotriazole
0.41 0.41 Pigment A 0.93 0.94 Byk .RTM. 307 0.01 0.01
1-Methoxy-2-propanol 36.26 64.67 2-Butanone 20.55 20.54 Ethyl
acetate 7.47 7.47 N,N-Dimethylacetamide 28.43 --
The imageable layer formulations were coated and dried to provide
an imageable layer coverage of 1.6 g/m.sup.2 on an
electrochemically grained and sulfuric-acid-anodized aluminum. The
substrate for Invention Example 7 was post-treated with a sodium
phosphate/sodium fluoride while the substrate for Comparative
Example 4 was post-treated with poly(vinyl phosphonic acid).
A 1.9 g/m.sup.2 oxygen barrier layer was provided by applying a 5%
solution of poly(vinyl pyrrolidone)/poly(vinyl alcohol) over the
imageable layer. The resulting imageable elements were imaged at a
series of exposures on a conventional Luxel Vx-9600 violet
platesetter and processed (bypassing the entry heater) using a
Glunz & Jensen Raptor 85 Polymer processor charged with Kodak
Polychrome Graphics T190-11 developer at 25.degree. C.
Uniform image densities were obtained for exposures ranging from 5
to 160 .mu.J/cm.sup.2 for the Invention Example 7 element. Uniform
image densities for the element of Comparative Example 4 were only
obtained at exposures greater than 100 .mu.J/cm.sup.2.
Invention Example 8
A UV-sensitive imageable layer formulation (composition of the
present invention) and imageable element were prepared as described
in Invention Example 7 except that the amount of Polymer A was
increased to 2.14 parts by weight. The imageable element was imaged
at 19 .mu.J/cm.sup.2 using a Luxel Vx-9600 violet platesetter and
was hand-processed using the T190-4 developer. The imaged printing
plate was mounted on a Komori Sprint 26 press and used to print
10,000 impressions with an abrasive ink containing 1.5% calcium
carbonate without showing a loss of print density in the solid
image areas.
The invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
* * * * *